The invention relates to an automatic selector device and, more particularly, to a multi-gear change-speed gearbox selector device in which a multi-way valve is arranged to activate selector actuators each used for one gear. The multi-way valve can be driven into several valve positions, each associated with one gear by a valve actuator whose operation depends on an electronic control unit. In these valve positions, the selector actuator exclusively associated with the appropriate gear is caused to take a selection action while the other selector actuators remain in a rest position.
In a selector device of the type shown in DE 27 44 286 Al, the manually selected gear range is evaluated in the electronic control unit which, as a result, itself suppresses from the selection the gears excluded by the gear range selected. A rotary spool of the multi-way valve is driven into its gear positions by a stepper motor controlled by the electronic control unit. The driving range selected by the driver is input into the control unit so that the stepper motor is prevented, within the control electronics, from being driven into the gear positions excluded from the driving range selected. If, for example, the control electronics should fail when driving on a gradient, while the driving range selected is limited to the two lower forward gears in order to utilize the engine braking effect and the other gears are consequently blocked electronically, the gearbox could adopt an uncontrolled driving condition because of the failure of the electronic blocking function.
Another type of hydraulic selector control device is shown in DE 21 26 910 Al for a vehicle with a multi-gear change-speed gearbox with plate clutches for the selection of the driving direction and the gears. These plate clutches are selected hydraulically and are located in the hydraulic circuit of a pressure medium generator. This selector control device has a manually actuated hydraulic multi-way spool whose housing has a rotary spool guided therein a sealed manner and, in the rotary spool, a longitudinal spool guided coaxially and in the longitudinal direction. These spools can be moved by a common manual lever such that two plate clutches can always be connected for one gear by the rotary spool via the housing connections and the respective plate clutch for the driving direction can be connected to the pressure medium generator by the longitudinal spool. In this selector control device, the longitudinal spool can -be fixed relative to the rotary spool by a spring catch device in a neutral position and in one position each for forward travel and reverse travel.
A control device of a different type for the hydraulic actuation of several selector clutches for motor vehicle change-speed gearboxes by a hydraulically adjustable selector control piston influencing the pressure medium supply to the selector clutches is shown in DE-AS 11 78 718. The adjustment force of this selector control piston is controlled by a mechanically actuated control spool located within the selector control piston. The control spool is guided in two hubs fixed on the housing and located within the selector control piston, independently of the selector control piston. This is intended to prevent the control spool from being carried along with the selector control piston in the presence of dirt and jamming, occurring as a result of the dirt, at the control edges and to prevent an undesired gear from being selected independently.
An object on which the present invention is based resides in being able to block gears by a manually actuated selector lever in an automatic selector device of a multi-gear change-speed gearbox in which the gear changes are initiated by an electronic control unit, it being necessary to satisfy the requirement for a mechanical connection between the selector lever and the hydraulic control system for the selector actuators operating by hydraulic pressure medium force in order to provide protection from a failure of the control electronics.
The foregoing object has been achieved in an advantageous manner by arranging an opposing stop so that it moves with a valve element, of the multi-way valve which valve element takes up in each of the gears an associated valve position relative to a valve housing. The position of a stop guided in its movement relative to the valve housing along the path of motion of the opposing stop can be fixed relative to the valve housing with respect to the valve positions to be blocked by a selector actuator which can be actuated manually.
In the selector device of the present invention, the stop actuatable by the manual selector lever interact with an opposing stop, which are connected as a function of the motion to the movable valve element of the multi-way valve such that the relative freedom of movement between these stops corresponds to the gear range selected.
In one embodiment of the present invention, the stop connected to the manual selector lever can be formed by a slot with which a sliding block connected to the movable valve element interacts. The stop can be configured such that the multi-way valve is mechanically prevented from being brought into the valve position for the selection of the reverse gear when only the forward gear range is made available by the selector lever.
The mechanical engagement of the stop device on the multi-way valve actuatable by the manual selector lever has priority over the actuation by the valve actuator whose operation depends on the electronic control unit. If the multi-way valve is driven by the stop into another position, the valve actuator is necessarily driven along with it in a corresponding manner because the stop and the opposing stop are in an opposing position relative to one another.